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UNSEGMENTED " WORMS." 



Parasitic in Man. 



Trichina. The formidable Trichina deserves fuller notice. It is best 

 known as a parasite in man, pig, and rat, but occurs also in hedgehog, 

 fox, marten, dog, cat, rabbit, ox, and horse. The sexual forms live in 

 the intestine, the female about 3 millimetres in length, the male about 

 half as long. After impregnation, the female brings forth numerous 

 embryos viviparously, 60 to So at a time, and altogether about 1500. 

 These bore through the wall of the intestine into the body cavity or 

 blood vessels, and work their way, especially through connective tissue, 

 to the muscle fibres. There they grow, coil themselves spirally, and 

 become encysted within a sheath, at first membranous and afterwards 

 calcareous. In these cysts, which may be sometimes counted in millions, 

 the young Trichinae remain passive, unless the flesh of their host be eaten 



